Hearing

Question 1

List the anatomy of the inner ear

Answer 1

Vestibula, Media and Tymphani (Scala) of the cochlear with the basilar membrane and the tectorial membrane. There are also inner and outer hair cells

Question 2

Describe responses to different frequencies in the cochlear

Answer 2

The apex is more floppy and therefore responds to low frequencies compared to the base which responds to higher frequencies

Question 3

Describe the Generation of hair movement in inner ear

Answer 3

The movement of the endolymph in response to sound will move over the inner hair cells. This will move the basilar membrane, which is attached to the tectorium membrane. The tectorium membrane is attached to outer hair cells via sterocillia. The outer hair cells will then also move via the sterocillia

Question 4

Describe molecular generation of the electrical impulses

Answer 4

Movement towards to higherst region of the hair cells (kinicillia) will open K+ channels. This will depolarize the cell causing Ca2+ influx and release of the NT glutamate to induce CNVIII to higher centres

Question 5

Why is K+ gradient important

Answer 5

K+ important for de and hyper polarisation of the hair cells, hence the difference in K+ concentrations between the media (high) and tymphani (low) is essential for this membrane potential

Question 6

Movement of hair to cause hyperpolarisation

Answer 6

Will be away from the kinocillia, however movement is not always proportional to the force of electrical impulse generated.

Question 7

pathway of auditory neurons

Answer 7

Will go from hair cells to CNVIII and then to the cochlear nucleus and then decussate to the superior olivary nucleus in the medulla. From there will project to the inferior colliculi of the midbrain. Will then follow the lateral lemniscus pathway to the medial geniculate nuclei of the thalamus. Will then pass to the auditory pathway in the temporal lobe (Brodman’s Area 41)

Question 8

How does the ear localize sound

Answer 8

There are two mechanisms in the superior olive nucleus, that utilize the lateral and medial regions and the trapezious region of the superior olive. Will use differences in loudness and timing to localise sound

Question 9

Describe how the Superior olive detects differences in Timing

Answer 9

There are different regions in the medial superior olive that connect to each ear. There will be differential stimulation of each region from each ear depending on which ear is activated first. The region that is activated the most will allow the brain to understand which side the sound comes from

Question 10

Describe how the Superior olive detects differences in loudness

Answer 10

The Trapezious will receive input from the ear proportional to loudness. It will also receive an inhibitory signal from the other ear proportional to loudness. Hence the balance of the two signals will then determine which side the sound originates from

Question 11

Discribe the auditory cortex

Answer 11

Different regions for frequencies

Question 12

What and Where pathway in auditory

Answer 12

There is a similar one to the visual pathway. There is also though to have a language region on the left side while music is thought to be on the right side of the brain